OGT Reference Provider


The equine metabolic syndrome (EMS) consists of a range of metabolic disorders predisposing horses and ponies to laminitis. The term insulin dysregulation describes an exacerbated insulin response to oral carbohydrates and may therefore involve incretin signalling. It is one of the central components of EMS alongside regional or generalized obesity.

Insulin resistance results from an altered response of peripheral tissues to insulin and is associated with insulin dysregulation. However, not every horse suffering from insulin dysregulation is insulin resistant. Therefore, diagnostic tests for EMS should not rely solely on insulin sensitivity.

Protocol for the oral glucose test (OGT):

  1. Let the horse fast overnight.
  2. Collect a basal blood sample.
  3. Administer 1 g glucose/kg bodyweight in 2L of water via nasogastric tubing.
  4. Collect a second sample around 120 min (maximal range 90 and 180 min). The horse should not be allowed to eat in the meantime.
  5. Analyze the samples for glucose and insulin. The latter should be measured using the Mercodia® Equine Insulin ELISA to ensure the obtention of a valid diagnosis based on the here provided reference range.

In contrast to tests like the combined glucose/insulin test (CGIT), this test has the advantage of being more practical to perform in a field environment and to assess postprandial hyperinsulinaemia under standardized conditions. Furthermore, in contrast to intravenous glucose infusion, enteral glucose can activate incretin signalling. Therefore, the OGT is better suited to detect insulin dysregulation than other test, while the other tests are more relevant for insulin resistance.

This web app is derived from a paper that tries to provide a more consistent reference range for insulin during the OGT. In addition, it alleviates the requirements on timing by providing a dynamic reference range for insulin at any time-point between 90 and 180 minutes, instead of 120 min only. The reference range is currently only available for insulin measured using the Mercodia® Equine Insulin ELISA. If you struggle finding a laboratory using this assay you can contact our partner laboratory.

Check insulin status

The measured insulin was µIU/mL. The sample was drawn min after glucose administration.

More information

Insulin dysregulation is a central part of the equine metabolic syndrome and can be detected using the OGT. However, it might also occur in horses affected by pituitary pars intermedia dysfunction (PPID), formerly known as equine Cushing syndrome. This is why horses that were found positive in the OGT and could be affected by PPID (age, other clinical signs) should also be tested (e.g. by TRH stimulation test), and if necessary treated, for this disease.

The management of patients with EMS mostly consists of an optimization of the diet and exercise. Energy intake has to be reduced gradually and adapted to the horse's actual needs, which are sometimes difficult to evaluate for the owner. Exercise is not limited to more intense training but also includes changes in the stables like access to a paddock, more space for social interaction or putting obstacles in the paddock to make the route from roughage to water circuitous etc. Specific advice and suggestions can be found in the literature.

Suggested readings:

For more details about the protocol recommended for use with these reference values please read following the paper:
Warnken T, Delarocque J, Schumacher S, Huber K, Feige K. Retrospective analysis of insulin responses to standard dosed oral glucose tests (OGTs) via naso-gastric tubing towards definition of an objective cut-off value. Acta Veterinaria Scandinavica 2018;60. doi:10.1186/s13028-018-0358-8.

Julien Delarocque wrote this web app upon an original idea from Tobias Warnken.